[4/?] - input+lnwallet: prepare input package for funding logic, add new MusigSession abstraction #7340

Roasbeef · 2023-01-19T04:15:09Z

Change Description

Depends on #7333 and #7331.

Only the last 3 commits are new. We'll also want to synchronize with #6974 as both the PRs update the deps to use the latest version of musig2.

In this PR, we first do a small refactoring to extract the musig2 session logic into a new package + struct. This allows use to re-use it later in tests w/o creating the entire wallet system.

Building on this, we then do some small prep to update the chanfunding package to be ready for the new musig2 channels.

The final change in this PR adds a new struct to encapsulate the new musig2 session logic for channels. A session can be created as soon as the verification nonce for the local party is known. At any time, we'll have two sessions: one for the remote commitment and one for the local commitment. A session can be finalized once the signing nonce (sent by the remote party) is known. When generating a signature, we'll use the remote party's verification nonce (the remote session), then generate a fresh nonce to complete the session. Similarly, when accepting a new state, we'll use the remote party's signing nonce to finalize the session, then verify the incoming signature.

For our local session, we'll use a counter-based system to generate the nonces we send to the remote party. The underlying counter here is the commitment height, which is then used by the existing shachain producer to generate fresh, but deterministic randomness. This lets us not have to store the secret nonce to disk, instead we'll just re-generate the nonce and use the sig we have on disk to combine, then create the final witness to broadcast.

The next PR in this series uses this PR, and its dependents to implement the funding logic within the wallet itself (reservations).

Steps to Test

Pull Request Checklist

Testing

Your PR passes all CI checks.
Tests covering the positive and negative (error paths) are included.
Bug fixes contain tests triggering the bug to prevent regressions.

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The change obeys the Code Documentation and Commenting guidelines, and lines wrap at 80.
Commits follow the Ideal Git Commit Structure.
Any new logging statements use an appropriate subsystem and logging level.
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ellemouton

First pass looks good! In my next pass I will spend more time understanding the details of the last commit

lnwallet/musession/manager.go

lnwallet/chanfunding/assembler.go

lnwallet/chanfunding/canned_assembler.go

lnwallet/musession/manager.go

lnwallet/chanfunding/canned_assembler.go

lnwallet/musig_session.go

yyforyongyu · 2023-02-17T12:42:38Z

lnwallet/musig_session.go

+// FromWireSig maps a wire partial sig to this internal type that we'll use to
+// perform signature validation.
+func (p *MusigPartialSig) FromWireSig(sig *lnwire.PartialSigWithNonce,
+) *MusigPartialSig {


nit: format

Gotta stamp something in the formatting guide here...

lnwallet/musig_session.go

input/musig2.go

lnwallet/musig_session.go

lntest/mock/signer.go

lnwallet/musig_session.go

Crypt-iQ

Pretty straightforward, will have to see how it fits in with the other changes

lnwallet/chanfunding/canned_assembler.go

input/test_utils.go

lnwallet/musession/manager.go

lnwallet/musig_session.go

yyforyongyu

I think we are missing unit tests here, can help with it if needed.

lightninglabs-deploy · 2023-05-31T15:04:23Z

@Roasbeef, remember to re-request review from reviewers when ready

Roasbeef · 2023-06-02T01:33:35Z

Initial set of review comment addressed. Will request review again after I put up the unit tests.

lnwallet/test_utils.go

Roasbeef · 2023-06-03T01:46:35Z

Unit tests added, PTAL!

funding/manager.go

input/musig2_session_manager.go

lnwallet/musig_session.go

yyforyongyu · 2023-06-06T12:32:41Z

lnwallet/musig_session.go

+	nonceOpts := []musig2.NonceGenOption{
+		musig2.WithPublicKey(m.localKey.PubKey),
+	}
+	if opts.customRand != nil {


I think we should enforce the check to make sure nonce is not repeated?

Hmm, how would we go about that? The customRand func in this case will use the new shachain root to derive nonces, also we'll start to pass in the txhash being signed into the nonce gen to further bind it.

We only set the custom rand for our local commitment, which means we only sign with this nonce when we go to broadcast.

Here's the argument I posted elsewhere for why imo the current approach is sound:

we only use that verification nonce to sign when we broadcast

we only ever have a single transaction valid to broadcast

after we sign and broadcast, we have that saved tx to rebroadcast, this tx never changes and we can't modify it (since we have another sig)

leaking the nonce needs us to sign with that key w/ two diff messages, which itself would mean we're broadcasting a revoked state

What I meant was, we'd make sure the opts is always set for m.commitType == localCommit, so maybe we can return an error if opts.customRand == nil && m.commitType == localCommit.

By design it's meant to be an optional value though, we maintain similar control flow, but then allow the caller to specify this. I think a better area to add additional protections would be the channel state machine itself (part 6 in this series) where this is used.

This would also break the current test that exercises the "normal" random nonce paths.

funding/manager.go

lnwallet/chanfunding/canned_assembler.go

lnwallet/musig_session.go

ellemouton

I think this is close!

lnwallet/musig_session.go

lnwallet/musig_session_test.go

yyforyongyu

This is good to go on my end once the redundant MuSig2Cleanup is handled.

yyforyongyu · 2023-06-08T13:42:01Z

lnwallet/musig_session.go

+	nonceOpts := []musig2.NonceGenOption{
+		musig2.WithPublicKey(m.localKey.PubKey),
+	}
+	if opts.customRand != nil {


What I meant was, we'd make sure the opts is always set for m.commitType == localCommit, so maybe we can return an error if opts.customRand == nil && m.commitType == localCommit.

yyforyongyu · 2023-06-08T13:47:36Z

lnwallet/musig_session.go

+
+	defer func() {
+		err := m.signer.MuSig2Cleanup(m.session.SessionID)
+		if err != nil {


I think MuSig2CombineSig will clean up the session so this will always return an error because the session is not found. Maybe we shouldn't do the auto cleanup in MuSig2CombineSig, or mention it in the method name or docs since it's error-prone.

Ah yeah good point, removed since it isn't necessary.

Initially I wanted to try to clean up the session as soon as possible, but realized that you need the session state present in order to do combine (so you can't clean up, then try to combine later the state won't be found). What I think we should do is add a defer CleanUp() in the link itself, so this way whenever we hang up the connection we remove the active session. We then also want to do this in the state machine after a round trip is complete.

I need to revisit the force close code in the final part of this PR, I think it ends up re-creating the session so it can properly force close.

ellemouton

LGTM pending @yyforyongyu 's comment re the session clean up 🥕 ⚡

(some linter things remain that I assume will be addressed in a final clean up commit once all the others are also in)

lnwallet/musig_session.go

In this commit, we extract the musig2 session management into a new module. This allows us to re-use the session logic elsewhere in unit tests so we don't need to instantiate the entire wallet.

In this commit, we update the set of intents and assemblers to recognize musig2. For this change, we use a new bool, `musig2`, then use that to determine if we need to use the new taproot funding scripts or not.

…tment state In this commit, we add a series of abstractions that'll allow us to easily do funding and also state updates for the new taproot channels. A partial session is defined by the knowledge of a verification nonce. Once the remote party sends a signature, we learn of their signing nonce, and can then complete a session. By using a JIT nonce approach, we ensure that the signer can generate their nonces randomly and also at the very last step to avoid having to maintain state. For our local nonces, we also have an option to use a counter based nonce derived from the shachain instead of fully random nonces. This allows us to not have to store ay additional state. Instead, when we need to go to broadcast, we can just regenerate the nonce then use that to broadcast.

In this commit, we eliminate some code duplication by removing the old `HashMutex` struct as it just duplicates all the code with a different type (uint64 and hash). We then make the main Mutex struct take a type param, so the key can be parametrized when the struct is instantiated.

By using the multimutex here, we'll no longer rely on a single mutex for the entire musig session set like we used to. Instead, we can use the session ID to key into a map of mutexes and use those directly.

Roasbeef · 2023-06-09T00:37:20Z

(some linter things remain that I assume will be addressed in a final clean up commit once all the others are also in

Really been fighting the linter on this one...should be ✅ now with the latest push.

yyforyongyu

Really been fighting the linter on this one...

Attack on linter series𖠆

LGTM🎉🎉🎉

Roasbeef added the taproot chans label Jan 19, 2023

Roasbeef mentioned this pull request Jan 20, 2023

[5/? ] - lnwallet: add taproot funding support to the internal wallet flow (reservations) #7344

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saubyk added this to the v0.16.0 milestone Jan 20, 2023

saubyk requested review from yyforyongyu and ellemouton January 25, 2023 20:04

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Roasbeef added 6 commits June 8, 2023 17:16

input+wallet: extract musig2 session management into new module

a2f7350

In this commit, we extract the musig2 session management into a new module. This allows us to re-use the session logic elsewhere in unit tests so we don't need to instantiate the entire wallet.

lnwallet/chanfunding: update assemblers to support musig2

02a0671

In this commit, we update the set of intents and assemblers to recognize musig2. For this change, we use a new bool, `musig2`, then use that to determine if we need to use the new taproot funding scripts or not.

input: use multmutex to increase concurrency for musig session manager

0bc8f3f

By using the multimutex here, we'll no longer rely on a single mutex for the entire musig session set like we used to. Instead, we can use the session ID to key into a map of mutexes and use those directly.

lnwallet: add initial unit test coverage for musig chan session

7c85f02

Roasbeef force-pushed the simple-taproot-funding branch from d22a0f9 to 7c85f02 Compare June 9, 2023 00:20

yyforyongyu approved these changes Jun 9, 2023

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Roasbeef merged commit a8dff96 into lightningnetwork:simple-taproot-chans-staging Jun 10, 2023

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[4/?] - input+lnwallet: prepare input package for funding logic, add new MusigSession abstraction #7340

[4/?] - input+lnwallet: prepare input package for funding logic, add new MusigSession abstraction #7340

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[4/?] - input+lnwallet: prepare input package for funding logic, add new MusigSession abstraction #7340

[4/?] - input+lnwallet: prepare input package for funding logic, add new MusigSession abstraction #7340

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Roasbeef commented Jan 19, 2023 • edited Loading

Change Description

Steps to Test

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Testing

Code Style and Documentation

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